The invention involves a radially expandable support structure for keeping open lumina within a body, in particular a blood vessel.
EP 0 335 341 B1 discloses, among other things, an expandable intraluminar vascular structure or prosthesis having at least one thin walled tube-shaped part with first and second ends and a wall surface arranged between the first and second ends, which has essentially the same thickness and several slits, which are directed essentially parallel to the longitudinal axis of the tube-shaped part. The tube-shaped part can have a first diameter, which makes the intraluminary transport of the tube-shaped part into a body passage that has a lumen possible, and the tube-shaped part can have a second, expanded and deformed diameter; such that a force directed radially outwardly can be applied from inside of the tube-shaped part and the second diameter is variable and depends on the amount of the force acting on the tube-shaped part, whereby the tube-shaped part is expanded and deformed in order to expand the lumen of the bodily passage. The vascular structure or the vascular prosthesis has several tube-shaped parts and at least one connection piece, which is arranged between tube-shaped parts that border each other, in order to connect tube-shaped parts, which are bordering each other, together with each other in a flexible manner.
A disadvantage in this intraluminary vascular structure is the relatively high radial rigidity of the individual parts, which noticeably impairs the flexibility necessary in a lumen for the prevention of internal injuries.
In U.S. Pat. No. 4,969,458, an intraluminary support structure is disclosed, which is made up of a spiral-shaped spring. Disadvantageous in this is the relatively high radial instability, which can lead to positions of undesired buckling.
From the aforementioned stems the problem of at least partially eliminating the disadvantages mentioned above using a new type of support structure. The resulting problem lies in particular in ensuring a high stability in the longitudinal direction with not too small of a radial rigidity, while avoiding a shortening of the support structure during radial expansion and while avoiding uncontrolled radial buckling movements.
This problem is solved according to the invention by a support structure according to the present invention.
The support structure according to the invention has a tube-shaped body that has at least two partial structures, with a wall surface that extends between a first and a second end, which has several cut out areas, in particular, slits, which are essentially oriented parallel to the longitudinal axis of the tube-shaped body. At least one partial structure runs without interruption in the axial direction almost, at least, from a first end to a second end of the tube-shaped structure. The first partial structure can be expanded at least in the radial direction and has at least one radial-expansion component, where the individual radial expansion components are arranged as a helix or in a helix shape. The second partial structure is almost rigid in the axial direction. The radial expansion component can be constructed to be closed, for example, oval, rectangular, rhomboidal, or elliptical in shape, or open, for example, in a meandering shape.
Through in particular this arrangement of the partial structures, it is achieved that during the radial expansion of the tube-shaped body, the second partial structure receives the thereby arising longitudinal forces. This has the result that the radial deformation is independent of the axial deformation and accordingly no shortening in the longitudinal direction occurs during the radial expansion. This is especially important during the invasive surgery, in order to create a desired supporting effect over a certain length.
In an advantageous manner, at least one partial structure has at least one meandering pattern, in order to increase the flexibility. This applies for the at least two partial structures.
It is advantageous that the loops of the meandering pattern are of varying sizes. This involves the elongation (amplitude) and/or wavelength, both in the radial as well as in the longitudinal direction of the support structure. Thus, on the whole a highly homogenous expandability relative to the first partial structure arises.
Furthermore, it is advantageous that the meandering pattern is a double meandering pattern, in order to increase the radial expandability.
The double meandering pattern is made advantageously of a first meandering pattern having loops and a second meandering pattern having larger or smaller loops than that of the first meandering pattern, in order, in this manner, to achieve at least an approximately uniform expansion during loading to cause radial expansion.
Furthermore, in an advantageous manner, a connection element that connects to the respective longitudinal end of the first radial expansion component is constructed as a loop-shaped stay. The stay prevents or lessens the possibility of the loops becoming spaced apart or rising out of the surface of the support structure when bending is required. Furthermore, when expanded, they improve the support action of the stent via a uniform surface.
In addition, it is advantageous when the wall surface has an essentially uniform thickness, in order to improve the homogeneous radial expansion.
The support structure can, for example, be made of a stainless steel that is suitable for medical purposes and/or have a biocompatible coating. Furthermore, any biocompatible material can be used as a material for manufacturing the stent, for example, tantalum, platinum, niobium, alloys and synthetic materials. The structures can be manufactured by laser cutting, electro-erosion, etching or even metal cutting.